Pressure sensor, object detection device, opening/closing device, and method for producing the pressure sensor

ABSTRACT

An object of the invention is to provide a pressure sensor, an object detecting system and an opening and closing system which realize the improvement in efficiency of sealing work on end portions of the pressure sensor and which are fabricated at low costs, as well as a pressure sensor fabricating method which requires no complex and troublesome steps.  
     A pressure sensor ( 17 ) includes a pressure sensing means (a piezoelectric sensor ( 33 )) for detecting a deformation due to an external force and a sensor accommodation body (a support means ( 35 )) which incorporates therein the pressure sensing means and which is made from a thermoplastic elastomer, and the sensor accommodation body is sealed off at at least one end portion thereof through a thermal treatment.

TECHNICAL FIELD

The present invention relates to a pressure sensor, an object detectiondevise and an opening/closing devise, and a method for producing thepressure sensor and, more particularly, to an improved technique forensuring that the sealing of a sensor end portion is implemented throughsimple work.

BACKGROUND ART

Conventionally, there have been disclosed a number types of pressuresensors including a pressure switch in which contacts are closed when anunknown pressure is applied thereto and a piezoelectric sensor whichemploys a piezoelectric element. In the piezoelectric sensor, when thepiezoelectric sensor is deformed by being pressed by an object, avoltage pulse is outputted from the piezoelectric sensor by virtue ofpiezoelectric effect, and whether or not an object is trapped isdetected based on the existence of this voltage pulse. When applyingthese types of pressure sensors to an object trapping preventive meansfor a powered window system of an automobile, a pressure switch or apiezoelectric sensor is arranged along, for example, a window frame of adoor, so that in the event that an object is trapped between the windowframe and a window glass, the pressure switch or piezoelectric sensor ismade to be deformed by the object. Then, when the window glass isclosed, in the event that the pressure switch is closed or apredetermined voltage pulse is outputted from the piezoelectric sensor,it is understood that an object is being trapped, and the rotationaldirection of an electric motor is reversed so as to release the objectfrom the trapped condition.

Then, with the pressure switch, in order to prevent the infiltration offoreign matters such as water drops, an end portion of the switch issealed through molding work in which the end portion is set in a mold ofa predetermined shape and a thermoplastic synthetic resin havinginsulating properties is injected into the interior of the mold whilebeing pressurized using a method substantially equivalent to aninjection molding or transfer molding (refer to Patent Document No. 1).

In addition, in a pressure switch like what has been described above,when loading a piezoelectric sensor into a support member for supportingthe sensor, the pressure sensor was inserted into a sensor accommodationhole formed in the support member, for example, after the insidediameter of the hole had been increased by sending air under pressureinto the sensor accommodation hole so as to expand the sensoraccommodation hole (refer to Patent Document Nos. 2, 3).

(Patent Document No. 1) JP-A-11-237289

(Patent Document No. 2) JP-A-11-72395

(Patent Document No. 3) JP-A-11-94656

However, since the sealing work done on the pressure switch was theworking method equivalent to the injection molding or transfer molding,there was caused a problem that the sealing work required long time tobe completed and was inefficient, and hence costs were increased.

In addition, when inserting the pressure sensor into the support memberbefore the sealing work, there was also caused another problem that longtime was necessary to send air into the sensor accommodation hole underpressure and equipment such as a squeeze pump was needed, and hence thefabricating work of the pressure sensor was inefficient.

The invention was made in view of the situations, and a primary objectthereof is to provide a low-cost pressure sensor, object detectingsystem and opening and closing system by making efficient the sealingwork that is done to seal the end portion of the pressure sensor. Inaddition, a secondary object of the invention is to provide a pressuresensor fabricating method which requires no complicated and troublesomesteps.

DISCLOSURE OF THE INVENTION

The objects can be attained by the following configurations.

(1) A pressure sensor including a pressure sensing means for detecting adeformation due to an external force and a sensor accommodation bodywhich is made from a thermoplastic elastomer and which covers an outsideof the pressure sensing means, wherein at least one end portion of thesensor accommodation body is sealed off through a thermal treatment.

(2) A pressure sensor as set forth under (1), wherein the pressuresensing means includes a plurality of electrodes which an output signalgenerated due to deformation is made to leave and a resistor providedportion where a resistor for detecting a disconnection or short-circuitof the electrode is provided, and wherein the resistor provided portionis fixedly sealed off through a thermal treatment at the one end portionof the sensor accommodation body.

(3) A pressure sensor as set forth under (2), wherein the resistorprovided portion includes at least one of a recessed portion, a raisedportion and a wedge-shaped portion which function to enhance the fixingstrength of the resistor provided portion when sealing off the endportion of the sensor accommodation body.

(4) A pressure sensor as set forth under (2), wherein the resistorprovided portion includes an insertion hole into which a pin is insertedfor enhancing the fixing strength to the sensor accommodation body.

(5) A pressure sensor as set forth under any of (1) to (4), wherein atleast one end portion of the pressure sensing means is covered by a capmade from a thermoplastic elastomer, and wherein the cap seals off theend portion of the sensor accommodation body.

(6) A pressure sensor as set forth under any of (1) to (5), wherein thesensor accommodation body is a support means for the pressure sensingmeans which is secured to a side where the sensor is mounted and fixed,wherein the support means includes a hollow portion which enhances thedeformation of the pressure sensing means when an external force isapplied, and wherein the hollow portion is sealed off through a thermaltreatment at at least one end portion of the support means.

(7) A pressure sensor as set forth under any of (1) to (5), wherein thesensor accommodation body includes a support means which is a coveringmeans for covering the pressure sensing means, which incorporatestherein the pressure sensing means covered by the covering means andwhich is secured to a side where the sensor is mounted and fixed,wherein the support means includes a hollow portion which enhances thedeformation of the pressure sensing means when an external force isapplied, and wherein the hollow portion is sealed off through a thermaltreatment at at least one end portion of the support means.

(8) A pressure sensor as set forth under (7), wherein the whole of atleast one end portion of the support means is covered by a cap made froma thermoplastic elastomer, and wherein the cap seals off the end portionwhen subjected to a thermal treatment.

(9) A pressure sensor as set forth under any of (1) to (8), wherein thepressure sensing means is formed using a composite piezoelectricmaterial resulting from a mixture of chlorinated polyethylene andpiezoelectric ceramic powder.

(10) A pressure sensor including a pressure sensing means for detectinga deformation due to an external force and a sensor accommodation bodywhich covers an outside of the pressure sensing means, wherein alubricant is loaded between the pressure sensing means and the sensoraccommodation body.

(11) A pressure sensor as set forth under (10), wherein at least one endportion of the sensor accommodation body is sealed off through a thermaltreatment.

(12) An object detecting system including the pressure sensor set forthunder any of (1) to (11) and a determination means for determining onthe contact of an object based on an output signal of the pressuresensor.

(13) An object detecting system as set forth under (12), wherein thedetermination means is fixedly sealed off through a thermal treatment atone end portion of a support means.

(14) An opening and closing system including the object detecting systemset forth under (12) or (13), a driving means for driving an opening andclosing portion and a control means for controlling the driving means insuch a manner as to stop a closing operation of the opening and closingportion or to operate the opening and closing portion to be opened whena determination means determines on the contact of an object with apressure sensor when the opening and closing portion is operated to beclosed.

(15) A pressure sensor fabricating method including a pressure sensingmeans for detecting a deformation due to an external force and a sensoraccommodation body which covers an outside of the pressure sensingmeans, the pressure sensor fabricating method including the steps ofmaking a lubricant adhere to at least either a surface of the pressuresensing means or an internal surface of the sensor accommodation bodyand inserting the pressure sensing means into the interior surface ofthe sensor accommodation body.

(16) A pressure sensor fabricating method as set forth under (15),wherein at least one end portion of the sensor accommodation body issealed off through a thermal treatment after the insertion of thepressure sensing means into the sensor accommodation body.

(17) A pressure sensor fabricating method as set forth under (15) or(16), wherein either zinc stearate or calcium carbonate is used as thelubricant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view of an object detecting system having apressure sensor according to the invention and an opening and closingsystem;

FIG. 2 a sectional view taken along the line A-A in FIG. 1 which showsconstructions of the object detecting system and the opening and closingsystem;

FIG. 3 is a cross-sectional view showing the construction of apiezoelectric sensor;

FIG. 4 is an external view of the piezoelectric sensor;

FIG. 5 is a block diagram of the object detecting system and the openingand closing system;

FIG. 6 is an explanatory drawing which shows a condition of the pressuresensor resulting when an object enters between a window frame and awindow glass to be trapped therebetween;

FIG. 7 shows characteristic charts depicting an output signal from afilter module, a determination output from a determination means and avoltage applied to a motor, respectively;

FIG. 8 shows explanatory drawings, in which (a) depicts a state beforesealing work is implemented on an end portion f the pressure sensor, (b)depicts a state in which sealing is implemented through vertical heatingand pressurization and (c) depicts a state in which sealing isimplemented through horizontal heating and pressurization, respectively;

FIG. 9 shows external views of support means, in which (a) is aperspective view showing a support means in which both end portions areopen, and (b) is a perspective view of a support means in which a sensoraccommodation hole is formed in one end portion thereof and a hollowportion therein is closed at the other end;

FIG. 10 is a sectional view showing the construction of a resistorprovided portion according to a first example;

FIG. 11 is a sectional view showing a condition in which the resistorprovided portion shown in FIG. 10 is inserted and thermally bonded inthe sensor accommodation hole in the support means;

FIG. 12 is a sectional view showing the construction of a resistorprovided portion according to a second example;

FIG. 13 shows drawings depicting the construction of a resistor providedportion according to a third example, in which (a) is a sectional viewof the resistor provided portion and (b) is a cross-sectional view takenalong the line B-B in (a);

FIG. 14 shows drawings depicting a condition in which the resistorprovided portion shown in FIG. 13 is inserted into the sensoraccommodation hole in the support means, in which (a) is an explanatorydrawing which shows a state before the insertion and (b) shows a statein which the resistor provided portion is secured with a pin after theinsertion;

FIG. 15 shows drawings depicting the construction of a resistor providedportion according to a fourth example, in which (a) is a sectional viewof the resistor provided portion and (b) is a side view thereof;

FIG. 16 shows drawings depicting a condition in which the resistorprovided portion shown in FIG. 15 is inserted into the sensoraccommodation hole in the support means, in which (a) is an explanatorydrawing showing a state before the insertion and (b) is an explanatorydrawing showing a state after the insertion;

FIG. 17 shows drawings depicting a condition in which heat seal isimplemented by filling a thermal plastic elastomer in the sensoraccommodation hole in the support means, in which (a) is a sectionalview showing a state before the heat seal and (b) is a sectional viewshowing a state after the heat seal;

FIG. 18 shows drawings depicting a condition in which the resistorprovided portion, which is caused to protrude from the sensoraccommodation hole in the support means, is covered by a cap for heatsealing, in which (a) is a partially sectional view showing a statebefore the cap is mounted, (b) is a partially sectional view showing astate after the cap has been mounted and (c) is a partially sectionalview showing a state after a heat seal has been carried out;

FIG. 19 is an external view of the support means shown in FIG. 18 whichshows a condition in which a cap is mounted at the other end thereof;

FIG. 20 shows drawings depicting conditions in which a support means anda piezoelectric sensor are integrally extrusion molded and end portionsthereof are sealed off, in which (a) is an external view showing a statein which a support means is cut out, (b) is an external view showing astate in which end portions of the support means are cut, (c) is anexternal view showing a state in end portions of a piezoelectric sensorare treated, and (d) is an external view showing a state in which theend portions of the piezoelectric sensor are covered by caps;

FIG. 21 is a sectional view showing a sealing construction on theresistor provided portion side;

FIG. 22 is a sectional view showing a sealing construction on thedetermination means side;

FIG. 23 shows explanatory drawings depicting conditions in which a capis fitted on a cap mounting allowance formed at an end portion of thesupport means and is then thermally bonded thereto, in which (a) is asectional view showing a state before the sealing and (b) is a sectionalview showing a state after the sealing;

FIG. 24 is a cross-sectional view showing an example of a pressuresensor installed in a support means having no hollow portion forenhancing a variation of the sensor;

FIG. 25 is a drawing showing the overall construction of a pressuresensor which constitutes one form of the pressure sensor having thecross-sectional construction shown in FIG. 24;

FIG. 26 is a cross-sectional view of a piezoelectric sensor in which nocovering layer is provided and hence an external electrode is exposed;

FIG. 27 shows drawings depicting constructions of the piezoelectricsensor shown in FIG. 26 resulting from conditions in which thepiezoelectric sensor is coated with a coating means, in which (a) is asectional view showing that both end portions the coating means are openand (b) is a sectional view showing that one end portion of the coatingmeans is closed; and

FIG. 28 shows explanatory drawings depicting conditions in which acoating means and a piezoelectric sensor are integrally extrusion moldedand end portions are sealed off, in which (a) is a sectional viewdepicting a state in which a piezoelectric sensor on the surface ofwhich a coating means is formed is cut to a predetermined length, (b) isa sectional view depicting a state in which the coating means is cut atend portions of the piezoelectric sensor, (c) is a sectional viewdepicting a state in which the end portions of the piezoelectric sensorare treated, and (d) is a sectional view depicting a state in which theend portions are sealed off by caps.

Note that in the drawings, reference numerals denote: 13 a widow frame(an opening); 15 a window glass (an opening and closing portion); 17 apressure sensor; 19 a determination means; 21 a driving means; 23 acontrol means; 25 a motor; 33, 111 piezoelectric sensors; 34 a sensoraccommodation hole; 35, 36 support means; 41 a hollow portion; 43 a sidewall portion; 45 a center electrode; 47 an external electrode; 49 acomposite piezoelectric material layer; 51 a covering layer; 53 aresistor provided portion; 55 a disconnecting detecting resistor; 63 adetermination module; 73 a control module; 75 an opening and closingswitch; 77 an object; 81 a conductive cap; 81 b a locking piece (awedge-shaped portion); 83 an irregular portion; 83 a a raised portion;83 b a recessed portion; 85, 87 insulating resins; 89, 91 insertionholes; 93 a pin; 95 a plug material; 97, 98, 101, 103, 107, 121, 123caps; 113, 115, 117 coating means; 100 an object detecting system; and150 an opening and closing system.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of a pressure sensor, an objectdetecting system and an opening and closing system, and a pressuresensor fabricating method according to the invention will be describedin detail by reference to the drawings.

FIG. 1 is a drawing showing external views of an object detecting system100 having a pressure sensor according to the invention and an openingand closing system 150 when they are used as part of a powered windowsystem of an automobile as one of application examples of the invention.FIG. 2 is a sectional view taken along the line A-A in FIG. 1. Note thatin FIG. 2, a right-hand side of the drawing represents the inside of apassenger compartment, whereas a left-hand side thereof represents theoutside of the passenger compartment.

Firstly, the basic construction of the object detecting system 100 ofthe embodiment is as follows. From FIG. 1, reference numeral 11 denotesa door of an automobile, reference numeral 13 denotes a window frame asan opening, and reference numeral 15 denotes a window glass as anopening and closing potion. Reference numeral 17 denotes a pressuresensor and is provided along a perimetric edge of an end portion of thewindow frame 13. Reference numeral 19 denotes a determination means fordetermining on the contact of an object to the pressure sensor 17 basedon an output signal of the pressure sensor 17.

In addition, the opening and closing system 150 of the embodimentincludes the object detecting system 100, a driving means 21 for openingand closing the window glass 15 and a control means 23 for controllingthe driving means 21. Here, the driving means 21 includes a motor 25, awire 27, a support device 29 for the window glass 15, a guide 13 and thelike and is constructed such that the wire 27 is moved by the motor 25,so that the support device 29 linked with the wire 27 is moved up anddown vertically along the guide 31, whereby the window glass 15 isopened and closed. Note that the driving means 21 is not limited to theone in which the wire 27 is used but driving means of other types may beadopted. In addition, the control means 23 and the motor 25 may beintegrated into a single unit.

As shown in FIG. 2, the pressure sensor 17 of the embodiment has aflexible piezoelectric sensor 33 as a pressure sensing means and asupport means 35 as a sensor accommodation body. The support means 35 isprovided with a deformable portion 37 which incorporates therein thepiezoelectric sensor 33 at a sensor accommodation hole 34 situated inthe vicinity of a lowermost portion thereof and which is secured to thewindow frame 13. This deformable portion 37 has a hollow portion 41 anda side wall portion 43. In addition, the support means 35 including thedeformable portion 37 is made of a thermoplastic elastomer (TPE) and hasa characteristic that it is softer than the piezoelectric sensor 33.Note that the deformable portion 37 may be integrated into aweatherstrip provided on the window frame 13. The pressure sensor 17 maybe constructed not only to be provided on the side of the opening butalso to be provided on the side of the opening and closing portion.

FIG. 3 is a cross-sectional view showing the cross-sectionalconstruction of the piezoelectric sensor 33. The piezoelectric sensor 33is made up of a center electrode 45 functioning as an electrode which asignal is caused to leave, an external electrode 47, a compositepiezoelectric material layer 49 which is made from a compositepiezoelectric material resulting from a mixture of a rubber elasticmaterial of chlorinated polyethylene and a sintered powder ofpiezoelectric ceramic and a covering layer 51, which are laminatedconcentrically so as to be formed into a cable-like shape and are thenpolarization treated, and the piezoelectric sensor 33 so made up has asuperior flexibility and generates an output signal according to theacceleration of a deformation. Sintered powders of leadlesspiezoelectric ceramic of, for example, lead titanate or leadtitanate-zirconate, bismuth-sodium titanate, sodium niobate andpotassium niobate are used as piezoelectric ceramic. The piezoelectricsensor 33 is fabricated via the following steps. Firstly, a chlorinatedethylene sheet and a (40 to 70) vol % piezoelectric ceramic (here, leadtitanate-zirconate) are uniformly mixed together into a sheet-like shapevia a rolling process. This sheet is cut minutely into pellets, andthereafter, these pellets are continuously extruded together with acenter electrode 45 to thereby form a composite piezoelectric materiallayer 49. Then, an external electrode 47 is wound around the compositepiezoelectric material layer 49. A covering layer 51 is alsocontinuously extruded in such a manner as to surround the externalelectrode 47. Finally, a direct current high voltage of (5 to 10) kV/mmis applied between the center electrode 45 and the external electrode 47so as to polarize the composite piezoelectric material layer 49.

When adding the piezoelectric ceramic powder to the chlorinatedethylene, the piezoelectric ceramic powder is preferably submerged in asolution of a titanium coupling agent and is then dried in advance. Bybeing treated like this, the surface of the piezoelectric ceramic powderis covered with a hydrophilic group and a hydrophobic group which arecontained in the titanium coupling agent. The hydrophilic group preventsthe aggregation of piezoelectric ceramic powders, and the hydrophobicgroup enhances the wetting characteristics between chlorinatedpolyethylene and piezoelectric ceramic powder. As a result, thepiezoelectric ceramic powder can be added uniformly to the chlorinatedpolyethylene in a large amount up to a maximum of 70 vol %. It has beenfound that a similar effect to what has just been described can beobtained by adding the titanium coupling agent while chlorinatedpolyethylene and piezoelectric ceramic powder are being rolled, in placeof submerging the piezoelectric ceramic powder in the titanium couplingagent. This treatment is superior in that the submerging treatment inthe titanium coupling agent is required particularly. Thus, chlorinatedpolyethylene also plays a role of a binder resin when piezoelectricceramic powder is mixed. Note that a non-halogen material such as athermoplastic elastomer may be used in place of chlorinatedpolyethylene.

While a normal metallic single-wire conductor such as a copper wire or astainless steel wire or a plurality of stranded conductors may be usedfor the center electrode 45, here, an electrode is used in which ametallic coil is wound around the circumference of an insulating polymerfiber. As the insulating polymeric fiber and the metallic coil, apolyester fiber which is commercially available in an electric blanketand a copper alloy containing 5 wt % of silver are preferable.

A belt-like electrode in which a metallic film is bonded onto apolymeric layer is used for the external electrode 47 and the externalelectrode 47 so formed is made to be wound around the circumference ofthe composite piezoelectric material layer 49. Then, polyethyleneterephthalate (PET) is used as the polymeric layer, and since anelectrode in which an aluminum film is bonded onto polyethyleneterephthalate has a high thermal stability at 120° C. and is massproduced commercially, it is preferable to use the electrode as theexternal electrode 47. In connecting this electrode to the determinationmeans 19, the electrode can be so connected by virtue of, for example,crimping or using a grommet. In addition, a construction may be possiblein which a metallic single-wire coil or a metallic braided wire is woundaround the aluminum film of the external electrode 47 so as to establisha conductivity therebetween, and the metallic single-wire coil or themetallic braided wire is soldered to the determination means 19. In thiscase, since soldering becomes possible, the working efficiency can bepromoted. In addition, a belt-like electrode may be used in which acopper film is formed on the PET layer, which enables soldering. Notethat the external electrode 47 is preferably wound around the compositepiezoelectric material layer 49 in such a manner as to partially overlapin order to shield the piezoelectric sensor from electric noise of theexternal environment.

While vinyl chloride or polyethylene may be used as the covering layer51, an elastic material such as a synthetic rubber and a thermoplasticelastomer which are superior in pliability and flexibility may be usedso as to facilitate the deformation of the piezoelectric sensor 33 whenpressed by an object. By adopting the constructions that have beendescribed heretofore, the minimum radius of curvature of thepiezoelectric sensor can be decreased to 5 mm. Note that the supportmeans 35 may be made to double as the covering layer 51, and as thisoccurs, the rationalization of components and fabrication steps can berealized.

As has been described heretofore, since the composite piezoelectricmaterial of the piezoelectric sensor has both the flexibility providedby chlorinated polyethylene and the high-temperature durability providedby piezoelectric ceramic, the reduction in sensitivity at hightemperatures inherent in a conventional piezoelectric sensor usingpolyvinylidene fluoride as the piezoelectric material can be eliminated,and since not only the durability at high temperatures is superior butalso no vulcanization step is required at the time of molding which isrequired in the case of a rubber such as EPDM, there can be obtained anadvantage that the production efficiency is improved.

FIG. 4 is an external view of the piezoelectric sensor 33, and aresistor provided portion 53, which incorporates therein a resistor fordetecting a disconnection and a short-circuit, is provided at one endportion of the piezoelectric sensor 33. The outside diameter of theresistor provided portion 53 is made to be substantially equal to theoutside diameter of the covering layer 51 of the piezoelectric sensor33, and the incorporated resistor is connected between the centerelectrode 45 and the external electrode 47. The resistor doubles as adischarge module which discharges electrical charges that are generatedin the piezoelectric sensor 33 by virtue of pyroelectric effect, whichrealizes the rationalization of components. The piezoelectric sensor 33is directly connected to the determination means 19, and thepiezoelectric sensor 33 and the determination means 19 are made integralwith each other. In addition, a cable 57 for supplying power supply andoutputting a detection signal and a connector 59 are connected to thedetermination means 19. When providing the piezoelectric sensor 33 inthe support means 35, the resistor provided portion 53, whichincorporates therein the resistor, is formed at one end portion, and thepiezoelectric sensor 33 is inserted into the sensor accommodation hole34. Thereafter, the piezoelectric sensor 33 and the determination means19 are connected to each other so as to be made integral with eachother. Alternatively, the piezoelectric sensor 33 may be inserted intothe sensor accommodation hole 34 in the support means 35 after theresistor provided portion 53 and the determination means 19 have beenconnected to the end portions of the piezoelectric sensor 33,respectively.

Here, when inserting the piezoelectric sensor 33, a method is taken inwhich the piezoelectric sensor 33 is inserted after a lubricant isapplied to at least either the piezoelectric sensor 33 or the sensoraccommodation hole 34. When this method is adopted, the piezoelectricsensor 33 can be smoothly inserted into the sensor accommodation hole 34by the action of the lubricant, whereby the production efficiency can beimproved without needing additional labor hours and adding any newequipment.

Namely, as a fabricating method of this pressure sensor, the followingsteps only have to be implemented in the order in which the steps aredescribe: a step of applying a lubricant to at least either the surfaceof the pressure sensing means or the internal surface of the sensoraccommodation body; a step of inserting the pressure sensing means intothe internal wall of the sensor accommodation body; and sealing off atleast one end portion of the sensor accommodation body through a thermaltreatment.

In addition, as the lubricant, it is possible to use zinc stearate andcalcium carbonate, which are used as a lubricant when extrusion moldingrubber and a lubricant for preventing the bonding of rubbers. Note thatthe lubricant is not limited to those materials described above but maybe selected from appropriate materials as required within such an extentthat materials used for the covering layer and the piezoelectric sensorare not deteriorated.

FIG. 5 is a block diagram of the object detecting system and the openingand closing system according to the embodiment. The determination means19 includes a voltage dividing resistor 61 for use in detecting adisconnection of the pressure sensor 17, a filter module 62 for allowingthe passage of only a predetermined frequency constituent from an outputsignal from the piezoelectric sensor 33, a determination module 63 fordetermining on the contact of an object to the pressure sensor 17 basedon an output signal from the filter module 62 and an abnormalitydetermination module 64 for determining on the disconnection abnormalityof the center electrode 45 and the external electrode 47 of thepiezoelectric sensor 33 from a voltage value that is formed by thedisconnection detecting resistor 55 and the voltage dividing resistor61.

In addition, a signal input module 65, which connects the centerelectrode 45 and the external electrode 47 to the determination means 19and inputs an output signal from the piezoelectric sensor 33 into thedetermination means 19, and a signal output module 66, which outputs adetermination signal from the determination module 63, are providedadjacent to each other within the determination means 19. A power supplyline to the determination means 19 and a ground line are also connectedto the signal output module 66. Furthermore, the determination means 19has a bypass module 67 such as a capacitor which is provided between thesignal input module 65 and the signal output module 66 for bypassing ahigh-frequency signal.

The respective constituent elements which make up the determinationmeans 19 are fabricated into a single IC chip so as to be installed on acircuit board, and the whole of the circuit board is incorporated into acylindrical or box-shaped shield case after having been electricallyinsulated. Then, the shield case electrically continues to the externalelectrode 47 of the piezoelectric sensor 33, as well as the ground lineof the power supply, and the piezoelectric sensor 33 and thedetermination means 19 are shielded altogether so as to prevent amalfunction by strong electric field noise. A further countermeasuresagainst strong electric field may be carried out by adding a feedthroughcapacitor and an EMI filter to an input/output module in the aforesaidcircuit.

The driving means 21 has a Hall element 68 for detecting a rotationalpulse of the motor 25.

The control means 23 is provided with a position detecting module 71 fordetecting an upper end position of the window glass 15 based on anoutput signal from the Hall element 68, an opening and closing portioncontact determination module 72 for determining on the contact of anobject to the window glass 15 by detecting the moving speed of thewindow glass 15 based on an output signal from the Hall element 68 and acontrol module 73 for controlling the motor 25 based on output signalsfrom the determination means 19, the position detecting module 71 andthe opening and closing portion contact determination module 72.

The position detecting module 71 counts and stores pulse signalsoutputted from the Hall element 68 so as to detect a current upper endposition of the window glass 15. Here, The upper end position Y of thewindow glass 15 is represented by a height from a lowest point of thewindow frame 13 as shown in FIG. 1.

The opening and closing portion contact determination module 72calculates the moving speed of the window glass 15 from pulse intervalsof pulse signals outputted from the Hall element 68 based on the factthat the moving speed of the window glass 15 slows when an object isbrought into contact with the window glass 15 and determines that anobject is brought into contact with the window glass 15 in the eventthat a variation |ΔV_(w)| per unit time of a moving time so calculatedbecomes greater than a preset value V_(w1) to thereby output pulsesignals of Lo->Hi->Lo. Here, of the pulse signals so outputted, thesignal of Hi level constitutes a determination signal.

In addition, an informing means 74 for informing a result ofdetermination by the determination means 19 via a predetermined light orthe like that is arranged on a front panel of a passenger compartmentand an opening and closing switch 75 for opening and closing the windowglass 15 are connected to the control means 23, and the opening andclosing switch 75 includes a one shot up switch and a one shot downswitch, which are designed to open and close the window glass via aone-touch operation, and a manual up switch and a manual down switch,which are designed to open and close the window glass 15 by beingmanually operated. Then, a power supply 76 is provided which is made upof an automotive battery which supplies electric power through thedetermination means 19.

The filter module 62 has filtering properties in which unnecessarysignals which are generated by vibrations or the like of a vehicle bodyof an automobile are removed from output signals from the piezoelectricsensor 33 and specific frequency constituents which appear in outputsignals from the piezoelectric sensor 33 are extracted. For thedetermination of filtering properties, the vibration properties of thevehicle body of the automobile and vibrations of the vehicle bodygenerated when running may only have to be analyzed for optimization.

Next, a basic operation when detecting the contact of an object with thepressure sensor 17 by the object detecting system will be described.

FIG. 6 shows a condition of the pressure sensor 17 resulting when anobject 77 enters to be trapped between the window frame and the windowglass. When the object 77 is brought into contact with the pressuresensor 17, a pressure by the object 77 is applied to the support means35 and the piezoelectric sensor 33. Since the support means 35 has morepliability than the piezoelectric sensor 33, the support means 35 is, asshown in the drawing, compressed about a point where the object 77 comesinto contact therewith by virtue of the pressure so applied, and theside wall portion 43 deforms, at the same time, the hollow portion 41being collapsed, whereby the piezoelectric sensor 33 is bent anddeformed about the point where the object 77 is brought into contactwith the support means 35.

When the piezoelectric sensor 33 is deformed like this, an output signalaccording to the acceleration of deformation is outputted from thepiezoelectric sensor 33 due to the piezoelectric effect. An outputsignal so outputted from the piezoelectric sensor 33 is then filtered bythe filter module 62. While there may occur a case where an outputsignal generated by an unnecessary vibration component attributed tovibrations of the vehicle body of the automobile appears in outputsignals from the piezoelectric sensor 33, the filter module 62 removesthis unnecessary signal.

Here, an example of an operating procedure of the determination module63 and the control module 73 will be described based on FIG. 7. FIG. 7shows characteristic drawings illustrating an output signal V from thefilter module 62, a determination output J of the determination means 19and an application voltage V_(m) to the motor 25. In FIG. 7, the axes ofordinates represent V, J and V_(m), respectively, from the top and theaxes of abscissas represent time t. When the one shot up switch of theopening and closing switch 75 is switched on at a time t₁, the controlmodule 73 applies a voltage of +V_(d) to the motor 25 so as to operatethe window glass 15 to be closed. In the event that the object 77 istrapped as shown in FIG. 6, a signal according to the acceleration of adeformation occurring on the piezoelectric sensor 33 is outputted fromthe piezoelectric sensor 33 due to the piezoelectric effect, and asignal according to the acceleration of the deformation of thepiezoelectric sensor 33 is caused to emerge from the filter module 62.As this occurs, in case the piezoelectric sensor 33 is made to beprovided simply on the window frame 13, the deformation of thepiezoelectric sensor 33 occurring when a trapping happens would besmall. In the case of this embodiment, however, as shown in FIG. 2,since the support means 35 has the pliability and the support means 35is easily compressed when a trapping happens, the amount of deformationof the piezoelectric sensor 33 is increased.

Then, since the hollow portion 41 is also collapsed while the trappingis occurring, the amount of deformation of the piezoelectric sensor 33is increased further. Thus, a large amount of deformation of thepiezoelectric sensor 33 is obtained, the acceleration, which is aquadratic differential value of deformation amount, becomes large, andas a result of this, an output signal of the piezoelectric sensor 33becomes large. The determination module 63 determines that a contactwith an object occurs in the event that the amplitude |V−V₀| of V fromV₀ is larger than D₀, and, as shown in FIG. 7(b), outputs pulse signalsLo->Hi (determination signal)->Lo as a determination output at a timet₂.

Given this determination signal, as shown in FIG. 7(c), the controlmodule 73 stops the application of the voltage of +V_(d) to the motor 25and applies a voltage of −V_(d) for a certain period of time until atime t₃ so as to cause the window glass 15 to drop a certain amount tothereby release the trapping or prevent the occurrence of a trapping. Inthe event that the pressure to the pressure sensor 17 is removed, asignal according to an acceleration by which the deformation iseliminated to restore an original condition (a signal component that issmaller than a reference potential V₀ in FIG. 7(a)) is outputted fromthe piezoelectric sensor 33.

Note that while whether V becomes larger or smaller than V₀ when thepressure sensor 17 is deformed changes depending on the bendingdirection and polarizing direction of the piezoelectric sensor 33, theallocation of electrodes (which to be made as a reference potential) andthe supporting direction of the piezoelectric sensor 33, since thedetermination module 63 determines on a trapping based on an absolutevalue of the amplitude from V₀ of V, a trapping can be determinedwhether V is larger or smaller than V₀.

Furthermore, since output signals which are outputted from thepiezoelectric sensor 33 as a result of the deformation of the pressuresensor 17 have different polarities depending on whether a deformationis generated or the deformation so generated is removed to restore anoriginal condition, it is possible to detect a contact of an object tothe pressure sensor 17 from the initiation to termination of thecontact, whereby the operation of the window glass can be forciblystopped, for example, while the trapping of an object is occurring andcan be resumed after the trapping has been eliminated.

Next, sealing work on an end portion of the pressure sensor 17 will bedescribed.

The support means 35 of the embodiment is made from thermoplasticelastomer. The thermoplastic elastomer is one of soft synthetic resinsand is a polymeric material having rubber-like elasticity in a coldcondition, and the composition thereof is such that a crosslinked rubberis dispersed in a resin. Since thermoplastic elastomer needs novulcanization step at the time of molding, there can be provided anadvantage that a good production efficiency can be obtained. Forexample, olefin (TPO), styrene (SBC), vinyl chloride (TPVC), urethane(TPU), ester (TPEE), amide (TPAE) and the like are raised as thethermoplastic elastomer.

As a method for incorporating the piezoelectric sensor 33 in the supportmeans 35, as has been described above, there are a method in which asupport means 35 is prepared as a single body through extrusion moldingor molding and a piezoelectric sensor is inserted into a sensoraccommodation hole 34 formed in the support means 35 in a later step,and a method in which a support means 35 and a piezoelectric sensor 33are extrusion molded at the same time.

Firstly, sealing work on an end portion of a pressure sensor preparedusing the former method will be described.

To carry out sealing work, as shown in FIG. 8, an end portion of thesupport means 35 is sealed off via the heat seal of thermoplasticelastomer by heating and pressurizing (heat treatment) the end portionof the support means 35 with a pressurizing jig. Namely, the sensoraccommodation hole and the hollow portion 41 are sealed off by heatingthe end portion while pressurizing the same from a state before it issealed off as shown in FIG. 8(a) in a vertical direction as shown in (b)or in a horizontal direction as shown in (c).

The pressurizing direction is selected appropriately depending on aplace where the pressure sensor 17 is laid out. In addition, the endportion can also be finished into a desired shape not only bypressurizing the end portion as it is but also by pressurizing the endportion while holding the same in a heating mold. When sealing off theend portion, it is preferable to seal off not only the sensoraccommodation hole 34 but also the hollow portion 41. Since thepiezoelectric sensor 33 is sealed in the interior of the support means35 through the sealing by the heat seal, there is no risk that foreignmatters such as water drops infiltrate the interior of the support means35, thereby making it possible to prevent the occurrence a malfunctionand corrosion which would otherwise be caused due to the filtration ofwater drops or the like. In addition, it is possible to prevent theoccurrence of a problem of a reduction in sensitivity due to thepressure sensor 17 being difficult to deflect or a failure of thesupport means 35 which would be caused when water drops infiltrate theinterior of the support means 35 to be frozen. Then, since an endportion of the piezoelectric sensor 35 is secured to the support means35, the piezoelectric sensor 33 can be securely accommodated within thesensor accommodation hole 34 in the support means 35 without anyloosening, thereby making it possible to eliminate a risk that thesensitivity of the sensor is reduced at the end portion of the sensor.Furthermore, in the construction that has been described above, thepressure sensor 17 may be constructed to be inserted into the sensoraccommodation hole 34 by taking a form in which the covering layer 51,which constitutes an outermost layer, is omitted so that the externalelectrode 47 is exposed to the outside.

Since the end portion of the support means 35 can be easily sealed offby heat treating the end portion through heating and pressurizing thesame, the working efficiency with which the sealing work is implementedon the end portion can be improved largely, whereby an efficient sealingcan be carried out at low costs when compared with a processing methodwhich is substantially equivalent to the injection molding and transfermolding. In addition, the support means 35 is not limited to a supportmeans which is made to open at both end portions thereof as shown inFIG. 9(a) but may be a support means in which the sensor accommodationhole 34 and the hollow portion 41 are closed at one end portion thereof.In the latter case, since only one end of the support means 35 needs tobe sealed off, the sealing work can be attained while omitting partthereof.

Next, examples of constructions of the resistor provided portion 53 willbe described below in which the configuration of the resistor providedportion 53 is improved in order to increase the fixing strength of theresistor provided portion 53 (refer to FIG. 4), which is provided at theend portion of the piezoelectric sensor 33, with respect to the supportmeans 35 when sealing off the end portion of the support means 35.

FIG. 10 is a sectional view illustrating a first example of theconstruction of a resistor provided portion 53.

The piezoelectric sensor 33 is constructed such that the compositepiezoelectric material layer 49 is formed on the surface of the centerelectrode 45, the external electrode 47 is formed on the surface of thecomposite piezoelectric material layer 49 in such a manner as to coverthe surface, and furthermore, the covering layer 51 is formed around thecircumference of the external electrode 47, and the covering layer 51 ispartially removed from the end portion of the piezoelectric sensor 33 soas to leave the external electrode 47 exposed thereat. Then, thedisconnection detecting resistor 55 is aligned in such a manner that alead wire direction becomes coaxial with the sensor, and a lead wire 56a situated on a side of the resistor which is closer to the sensor isconnected to the center electrode 45. On the other hand, a lead wire 56b situated on an opposite side of the resistor is connected to a bottomportion 81 a of a cylindrical conductive cap 81 having a diameter whichenables the conductive continuity of the cap with the external electrode47 at an end portion thereof. An electrical connection between the leadwire 56 a and the center electrode 45 and an electrical connectionbetween the lead wire 56 b and the conductive cap 81 can be implementedby an appropriate connection means such as welding, brazing andcrimping.

The conductive cap 81 is made of a metal or the like, and an insulatingresin 85 having a step-like irregular portion 83 is secured to anexternal surface of the conductive cap along the axial direction of thesensor. The irregular portion 83, which is illustrated as an example, issuch that a plurality of raised portions 83 a, which protrude radiallyoutwards of the conductive cap 81, and recessed portions 83 b are formedalong a circumferential direction of the conductive cap 81. Note that inthe event that there exists no risk that the resistor provided portion53 is brought into electrical contact with its surroundings after it hasbeen secured in the support means 35, in place of forming the insulatingresin 85, the conductive cap 81 itself may be made to have the irregularportion 83 on an outer circumferential surface thereof.

According to the resistor provided portion 53 that is constructed as hasbeen described above, as shown in FIG. 11, when the piezoelectric sensor33 is inserted into the sensor accommodation hole 34 for heat seal, theirregular portion 83 on the piezoelectric sensor 33 side bites into thesensor accommodation hole 34 to thereby ensure the prevention of theaxial slide or dislocation of the piezoelectric sensor 33 within thesensor accommodation hole 34, whereby the piezoelectric sensor 33 can bedisposed within the sensor accommodation hole 34 without any loosening,thereby making it possible to enhance the sensitivity of the sensorwithout dulling the deformation acceleration of the piezoelectric sensor33 once an object is brought into contact with the piezoelectric sensor33.

FIG. 12 is a sectional view illustrating a second example of theconstruction of a resistor provided portion 53. In the followingdescription, like reference numerals are given to like members havinglike functions to those that have been described above, and thedescription thereof will be omitted.

In this example of construction, an insulating resin 87 having an angledirregular portion 83 which diametrically expands and contracts along theaxial direction of the sensor is secured to an external surface of aconductive cap 81.

Also, according to this construction of the resistor provided portion53, the irregular portion 83 on the piezoelectric sensor 33 side bitesinto the sensor accommodation hole 34, whereby it is possible to ensurethe prevention of the axial slide or dislocation of the piezoelectricsensor 33 within the sensor accommodation hole 34. In addition, sincethe shape of the irregular portion 83 is simple, the working of theinsulating resin 87 becomes easy. Note that the irregular portion 83 isnot limited to the angled one but may be formed into a conical shapewhich diametrically expands as it extends towards an end portion thereofalong the axial direction of the sensor or a conical shape whichdiametrically contracts as it extends from a diametrically expandedportion towards an end portion thereof, and a similar advantage can beobtained even with either of the conical shapes.

FIG. 13(a) is a sectional view illustrating a third example of theconstruction of a resistor provided portion 53 and FIG. 13(b) is across-sectional view taken along the line B-B in FIG. 13(a).

In this example of construction, an insertion hole 89 is provided to beopened in part of an outer circumferential surface of a conductive cap81 so that a fixing pin is passed through the conductive cap 81 via theinsertion hole 89 so provided. According to the resistor providedportion 53 that is constructed as has been described above, an insertionhole 91 is provided to be opened in advance in a position on the sensoraccommodation hole 34 in the support means 35 so that the fixing pin isinserted thereinto, as shown in FIG. 14(a), and the insertion holes 89,91 are aligned with each other, as shown in FIG. 14(b), so that a pin 93is inserted into the insertion holes 89, 91, whereby the resistorprovided portion 53 is fixed to the support means 35 and thepiezoelectric sensor 33 can be disposed within the sensor accommodationhole 34 without any loosening, a similar advantage to that describedabove thereby being provided.

Note that the piezoelectric sensor 33 is inserted into the sensoraccommodation hole 34 without providing the insertion hole 91 in thesupport means 35 side, so that a pin having a sharp point at a distalend thereof may be made to pierce the support means 35 so as to beinserted into the insertion hole 91 of the conductive cap 81. In thisconstruction, the fixing of the resistor provided portion 53 to thesupport means 35 can be ensured more easily.

FIG. 15(a) is a sectional view illustrating a fourth example of theconstruction of a resistor provided portion 53 and FIG. 15(b) is a sideview thereof.

In this example of construction, a dislocation preventing locking piece(a wedge portion) 81 b is provided on a conductive cap 81 in such amanner as to protrude outwards from a bottom portion 81 side, whichfunctions as a proximal portion, towards a piezoelectric sensor 33 sideto thereby be formed into a wedge shape. Here, as an example, part of acircumferential surface of the conductive cap 81 is cut out in the axialdirection as a locking piece 81 b, and the locking piece 81 b is thendrawn outwards from the bottom portion 81 a side, which functions as aproximal end, whereby the locking piece 81 b is formed. Note that whilea pair of upper and lower locking pieces 81 b are provided in thisexample, more than two locking pieces or a single locking piece may beprovided, and the locking piece so provided may be constructed into amultiplicity of steps developed along the axial direction.

According to the resistor provided portion 53 that is constructed as hasbeen described above, as shown in FIG. 16, when the piezoelectric sensor33 is inserted into the sensor accommodation hole 34 in the supportmeans 35 for heat seal, the locking pieces 81 bite into the sensoraccommodation hole 34 to thereby ensure the prevention of the axialslide or dislocation of the piezoelectric sensor 33 within the sensoraccommodation hole 34, whereby a similar advantage to that describedabove can be provided.

Next, another method will be described in which the resistor providedportion 53 is sealed within the support means 35.

FIG. 17 shows explanatory drawings illustrating how a thermoplasticelastomer is filled in the sensor accommodation hole in the supportmeans for heat seal, in which FIG. 17(a) is a sectional viewillustrating a condition before heat seal and FIG. 17(b) is a sectionalview illustrating after heat seal.

Here, as shown in FIG. 17(a), while the piezoelectric sensor 33 isinserted into the sensor accommodation hole 34 in the support means 35,a plug material 95 made from thermoplastic elastomer is filled in thesensor accommodation hole 34 in the support means 35 for clogging thesensor accommodation hole 34. When a heat seal is implemented in thisstate, the plug material 95 clogs the sensor accommodation hole 34 inthe end portion of the support means 35 without any gap as shown in FIG.17(b), and the resistor provided portion 53 at the distal end of thesensor is secured to the plug material 95 and the support means 35within the support means 35, whereby the piezoelectric sensor 33 can besealed in the interior of the support means 35 in an ensured fashionthrough a simple operation.

Furthermore, there exists the following method as another sealingmethod.

FIG. 18 shows explanatory drawings illustrating how the end portion ofthe support means is sealed off using a cap made from thermoplasticelastomer.

In a state in which the resistor provided portion 53 is disposed in thesensor accommodation hole 34 as shown in FIG. 18(a), a cap 97 is mountedwhich is made from thermoplastic elastomer and which covers the whole ofthe end portion of the support means 35, and a heat seal is implementedon the end portion by heating and pressurizing (a thermal treatment) thevicinity of the cap 97, whereby since the sensor accommodation hole 34and the hollow portion 41 of the support means 35 are closed in anensured fashion and the end portion thereof is covered by the cap 97,the bonding strength is enhanced, so that the durability is increased.

In addition, as shown in FIG. 19, the entirety of the pressure sensorcan be sealed off by similarly mounting a cap 98 made from thermoplasticelastomer to the other end of the support means 35 in such a manner asto cover the entirety of the relevant end portion

Next, sealing work on an end portion of a pressure sensor prepared by amethod for extrusion molding a support member 35 and a piezoelectricsensor 33 together.

FIG. 20 shows explanatory drawings illustrating a way in which a supportmeans and a piezoelectric sensor are extrusion molded integrally and endportions thereof are sealed off.

As shown in FIG. 20, when a predetermined length is cut out of a supportmeans 35 which is continuously molded in such a state that apiezoelectric sensor 34 is inserted therein so as to prepare a pressuresensor, end portions thereof will be sealed off as follows. Firstly, endportions of a support means 35 which has been so cut out as shown inFIG. 20(a) are cut while the piezoelectric sensor 33 is left as it is asshown in FIG. 20(b), so that the piezoelectric sensor 33 is made toprotrude from the sensor accommodation hole 34. Then, as shown in FIG.20(c), the resistor provided portion 53 and the determination means 19,which are shown in FIG. 4, are mounted on end portions of the protrudingpiezoelectric sensor 33, and the end portions are sealed off by caps101, 103, respectively, as shown in FIG. 20(d).

Here, specific sealing constructions will be described by showing asectional view taken along a direction C in FIG. 20(d) in FIG. 21 and asectional view taken along a direction D in FIG. 22, respectively.Namely, FIG. 21 is a sectional view illustrating a sealing constructionon the resistor provided portion 53 side, whereas FIG. 22 is a sectionalview illustrating a sealing construction on the determination means 19side.

As shown in FIG. 21, on the side of the resistor provided portion 53,the resistor provided portion 53 is mounted on the end portion of thepiezoelectric sensor 33 which is made to protrude from the support means35, and the outside of the resistor provided portion 53 and the whole ofthe end portion of the support means 35 are covered by the cap 101 madefrom thermoplastic elastomer for heat seal.

In addition, as shown in FIG. 22, on the side of the determination means19, the determination means 19 which is formed on the circuit board ismounted on the end portion of the piezoelectric sensor 33 which is madeto protrude from the support means 35, and the outside of thedetermination means 19 and the whole of the end portion of the supportmeans 35 are covered by the cap 103 made from thermoplastic elastomerfor heat seal.

Since the sealing work on the end portions by thermal treatment can beimplemented simply by virtue of the sealing constructions at the endportions of the piezoelectric sensor that have been described justabove, the operation for sealing off the end portions is simplified andhence the reduction in costs can be realized.

In addition, as shown in FIG. 20, the covering layer 51 (refer to FIG.3) of the piezoelectric sensor 33 can be omitted even in the event thatthe support means 35 and the piezoelectric sensor 33 are extrusionmolded together. Sealing work on end portions of the support means 35 somolded can be implemented in a similar manner to what has been describedabove. In addition to this method, there is, for example, another methodin which when removing an end portion of the support means 35, part ofthe support means 35 which exists around the sensor accommodation hole34 is left so as to constitute a cap mounting allowance 105, and aninner circumferential portion of a cap 107 made from thermoplasticelastomer is fitted on the cap mounting allowance 105 for heat seal sothat the end portion of the support means 35 can be sealed off. On theother hand, a hollow portion 14 in the support means 35 is heat sealedat the end portion of the support means 35 by heating and pressurizing(thermal treatment) the relevant end portion of the support means 35. Byimplementing the sealing work on the end portion using the cap 107 whichhas a small volume, the material can be reduced to thereby realize thereduction in production costs.

Any of the pressure sensors 17 that have been described heretofore issuch as to be incorporated in the support means 35 having the hollowportion 41 which is intended to increase the amount of deformation ofthe sensor. The application of the pressure sensor according to theinvention is not limited to the form of the support means, and thepressure sensor of the invention may be incorporated in a support meanswhich does not have the aforesaid hollow portion 41. An example of apressure sensor having such a construction is shown in FIG. 24, which isa sectional view. A pressure sensor 17 shown in FIG. 24 is constructedsuch that a piezoelectric sensor 33 is incorporated in the interior of asupport means 36 made from thermoplastic elastomer and havingsubstantially a cylindrical cross section. FIG. 25 is a drawing showingthe overall construction of a form of a pressure sensor having the crosssectional construction shown in FIG. 24, in which the pressure sensor ismade up by incorporating the piezoelectric sensor 33 to which a resistorprovided portion 53 and a determination means 19 are connected in thetubular support means 36 made from thermoplastic elastomer. As to thesealing of an end portion of the support means 36, there is a method inwhich a bag-like tube is placed over as shown in the drawing for heatseal. In addition to this method, there exist appropriate methods to beadopted including one in which a cap is placed for heat seal.

According to the pressure sensor 17 provided with the support means 36which is constructed as has been described above, by mounting thepressure sensor 17 at a desired disposition position in an appropriateform to the purpose of a detection, a desired detection can beimplemented. Then, an extent to which the deformation of thepiezoelectric sensor 33 due to tensile, compression, bending or twistingforce acting thereon is attenuated is reduced due to the support portion36 being thin, and the detection sensitivity of the acceleration of adeformation is increased, thereby making it possible to realize adetection with high sensitivity. In addition, since the diameter of thesensor is small, whereby the sensor can be made small in size, thedegree of freedom in placing the sensor and the degree of freedom indesigning in an attempt to incorporate the sensor in other members areimproved, so that the scope of the application of the pressure sensoraccording to the invention can be expanded.

Next, as a further form of a pressure sensor according to the invention,a form will be described in which a piezoelectric sensor is just coveredwithout providing a support means.

FIG. 26 shows a cross-sectional view of a piezoelectric sensor which hasno covering layer and in which an external electrode 47 is exposed, andFIG. 27 shows drawings illustrating constructions in which thepiezoelectric sensor shown in FIG. 26 is covered with a covering meansmade from thermoplastic elastomer.

A pressure sensor shown in FIG. 27(a) is such as to be formed byinserting a piezoelectric sensor 111 to which a resistor providedportion 53 and a determination means 19 are connected into a coveringmeans 113 functioning as a sensor accommodation body which is formedinto a tube-like shape which is made to open at both end portionsthereof. The end portions are sealed off by heat sealing the endportions of the covering means 113 in directions indicated by arrows inthe drawing.

In addition, a pressure sensor shown in FIG. 27(b) is constructed byinserting the piezoelectric sensor 111 to which the resistor providedportion 53 and the determination means 19 are connected into a tube-likecovering means 115 which is closed at one end portion thereof. The endportion is sealed off by heat sealing the one end portion of thecovering means 113 as indicated by arrows in the drawing. In this case,since only the one end of the covering means 113 needs to be sealed off,a sealing operation can be omitted. In addition, as to the sealing workon the end portion, in addition to the heat sealing of the end portionwithout any additional process, the end portion may be sealed off byplacing a cap made from thermoplastic elastomer over the end portion forheat seal.

Thus, by constructing the pressure sensor using a minimum requirednumber of members and sealing off the end portion of the covering meansthrough heat seal, the low-cost pressure sensor can be obtained whichprevents the infiltration of foreign matters such as water drops intothe interior of the sensor.

Next, a pressure sensor having a piezoelectric sensor which is coveredover the surface thereof by a covering means will be described by takingfor example a case where a piezoelectric sensor and a covering means areextrusion molded integrally.

FIG. 28 shows explanatory drawings illustrating a way in which acovering means and a piezoelectric sensor are extrusion moldedintegrally and end portions thereof are sealed off.

As shown in FIG. 28(a), a piezoelectric sensor 111 in which a coveringmeans 117 is formed from thermoplastic elastomer on the surface thereofthrough extrusion molding is cut to a predetermined length, and thecovering means 117 at end portions of the piezoelectric sensor 111 iscut as shown in FIG. 28(b) so as to allow an external electrode at theend portions of the piezoelectric sensor 111 to be exposed. Then, asshown in FIG. 28(c), the resistor provided portion 53 and thedetermination means 19, which are shown in FIG. 4, are mounted to endportions of the piezoelectric sensor 117 and are, for example, as shownin FIG. 18(d), then sealed off by caps 121, 123, respectively.

Thus, the pressure sensor which prevents the infiltration of foreignmatters such as water drops into the interior of the sensor through thesimple operation in which the end portions of thereof are sealed offafter the covering member and the piezoelectric sensor have beenprepared integrally through extrusion molding and the resistor providedportion 53 and the determination means 19 have been mounted thereon.

The application of the pressure sensors according to the invention thathave been described heretofore is not limited to the pressure sensorthat is to be provided in the window frame of the automobile, but thepressure sensors may be applied to a sliding door in a side of thevehicle body of the automobile, a powered sunroof in the ceiling of thevehicle body, and a powered hatch door at the rear of the vehicle body,or to a powered trunk lid, a gull-wing door and an automatic opening andclosing wing of a truck, and a similar advantage to what has beendescribed before can be provided. In addition, the pressure sensors ofthe invention can also equally be applied not only to automobiles butalso to railway cars or automatic doors in buildings. In addition, thepressure sensors of the invention can also be applied to a bumper sensorsystem for moving vehicles such as automatic guided vehicles andautomobiles.

Note that the constructions of the respective embodiments may becombined as appropriate for use, and as to the insertion of the pressuresensing means into the sensor accommodation body, a similar function andeffectiveness can be provided even in the event that the material of thesensor accommodation body is not limited to thermoplastic elastomer butother materials may be used.

While the invention has been described in detail and by reference to thespecific embodiments, it is clear to those skilled in the art thatvarious changes and modifications can be made thereto without departingfrom the spirit and scope of the invention.

The subject patent application is based on the Japanese PatentApplication No. 2003-016404 filed on Jan. 24, 2003 and the contentsthereof is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

According to the invention, since the sensor accommodation body whichaccommodates therein the pressure sensing means is made fromthermoplastic elastomer and end portions thereof can easily be worked tobe sealed off by thermally treating the sensor accommodation body, thepressure sensor, object detecting system and opening and closing systemcan be provided which realize the improvement in efficiency of thesealing work on the end portions and which are fabricated at low costs.

In addition, the pressure sensor can be fabricated without needingcomplex and troublesome steps by inserting the pressure sensing meansinto the internal surface of the sensor accommodation body with thelubricant being applied to at least either the surface of the pressuresensing means or the internal surface of the sensor accommodation body.

1. A pressure sensor comprising pressure sensing means for detecting adeformation due to an external force and a sensor accommodation bodywhich is made from a thermoplastic elastomer and which covers an outsideof the pressure sensing means, wherein at least one end portion of thesensor accommodation body is sealed off through a thermal treatment. 2.A pressure sensor as set forth in claim 1, wherein the pressure sensingmeans comprises a plurality of electrodes which an output signalgenerated due to deformation is made to leave and a resistor providedportion where a resistor for detecting a disconnection or short-circuitof the electrode is provided, and wherein the resistor provided portionis fixedly sealed off through a thermal treatment at the one end portionof the sensor accommodation body.
 3. A pressure sensor as set forth inclaim 2, wherein the resistor provided portion includes at least one ofa recessed portion, a raised portion and a wedge-shaped portion whichfunction to enhance the fixing strength of the resistor provided portionwhen sealing off the end portion of the sensor accommodation body.
 4. Apressure sensor as set forth in claim 2, wherein the resistor providedportion comprises an insertion hole into which a pin is inserted forenhancing the fixing strength to the sensor accommodation body.
 5. Apressure sensor as set forth in claim 1, wherein at least one endportion of the pressure sensing means is covered by a cap made from athermoplastic elastomer, and wherein the cap seals off the end portionof the sensor accommodation body.
 6. A pressure sensor as set forth inclaim 1, wherein the sensor accommodation body is support means for thepressure sensing means which is secured to a side where the sensor ismounted and fixed, wherein the support means comprises a hollow portionwhich enhances the deformation of the pressure sensing means when anexternal force is applied, and wherein the hollow portion is sealed offthrough a thermal treatment at at least one end portion of the supportmeans.
 7. A pressure sensor as set forth in claim 1, wherein the sensoraccommodation body comprises support means which is covering means forcovering the pressure sensing means, which incorporates therein thepressure sensing means covered by the covering means and which issecured to a side where the sensor is mounted and fixed, wherein thesupport means comprises a hollow portion which enhances the deformationof the pressure sensing means when an external force is applied, andwherein the hollow portion is sealed off through a thermal treatment atat least one end portion of the support means.
 8. A pressure sensor asset forth in claim 7, wherein the whole of at least one end portion ofthe support means is covered by a cap made from a thermoplasticelastomer, and wherein the cap seals off the end portion when subjectedto a thermal treatment.
 9. A pressure sensor as set forth in claim 1,wherein the pressure sensing means is formed using a compositepiezoelectric material resulting from a mixture of chlorinatedpolyethylene and piezoelectric ceramic powder.
 10. A pressure sensorcomprising pressure sensing means for detecting a deformation due to anexternal force and a sensor accommodation body which covers an outsideof the pressure sensing means, wherein a lubricant is loaded between thepressure sensing means and the sensor accommodation body.
 11. A pressuresensor as set forth in claim 10, wherein at least one end portion of thesensor accommodation body is sealed off through a thermal treatment. 12.An object detecting system comprising the pressure sensor set forth inclaim 1 and determination means for determining on the contact of anobject based on an output signal of the pressure sensor.
 13. An objectdetecting system as set forth in claim 12, wherein the determinationmeans is fixedly sealed off through a thermal treatment at one endportion of support means.
 14. An opening and closing system comprisingthe object detecting system set forth in claim 12, driving means fordriving an opening and closing portion and control means for controllingthe driving means in such a manner as to stop a closing operation of theopening and closing portion or to operate the opening and closingportion to be opened when determination means determines on the contactof an object with a pressure sensor when the opening and closing portionis operated to be closed.
 15. A pressure sensor fabricating methodcomprising pressure sensing means for detecting a deformation due to anexternal force and a sensor accommodation body which covers an outsideof the pressure sensing means, the pressure sensor fabricating methodincluding the steps of making a lubricant adhere to at least either asurface of the pressure sensing means or an internal surface of thesensor accommodation body and inserting the pressure sensing means intothe interior surface of the sensor accommodation body.
 16. A pressuresensor fabricating method as set forth in claim 15, wherein at least oneend portion of the sensor accommodation body is sealed off through athermal treatment after the insertion of the pressure sensing means intothe sensor accommodation body.
 17. A pressure sensor fabricating methodas set forth in claim 15, wherein either zinc stearate or calciumcarbonate is used as the lubricant.